1. Field of the Invention
The present invention relates to flat panel display devices, and more particularly, to a flexible substrate which simplifies a fabrication process and prevents deformation, and a method for fabricating a flexible display device having the same.
2. Discussion of the Related Art
Currently, display device markets have become markets of flat display devices. Also, increased use of flat display devices has allow for easier fabrication of large size and light weight devices. Flat display devices include liquid crystal display devices LCD, plasma display panel PDP, organic electroluminescence display device OLED, and the like. Flat display devices use glass substrates as supporting bodies for supporting a plurality of thin films. However, there are problems associated with the use of glass substrates. In particular, thinner glass substrates are susceptible to breakage due to reduced durability and limited flexibility.
Recently, instead of using the glass substrate, which has poor durability and flexibility, a flexible display device has been developed that uses a substrate material that is thin, but also has long durability, such as plastic or metal foil.
FIGS. 1A and 1B illustrate a method for fabricating a substrate of a flexible display device according to the related art.
As shown in FIG. 1A, an overcoat layer 4 is applied to a flexible substrate 2 of stainless steel. The overcoat layer 4 serves to flatten the flexible substrate 2 of stainless steel. Then, thin arrays 6 of the display device are formed on the overcoat layer 4. Here, flexible substrate 2 has a first height h1. As shown in FIG. 1B, a back side of the flexible substrate 2 is then etched to be a second height h2, which is less than the first height h1, to finish fabrication of the flexible display device. However, the flexible display device fabricated by a fabrication process of FIGS. 1A and 1B has a problem in that the step for forming the overcoat layer 4 and the step for etching the back side of the flexible substrate 2 are complicated.
To solve the above problem, a flexible display device is formed by a fabrication process shown in FIGS. 2A and 2B. FIGS. 2A and 2B illustrate another method for fabricating a substrate of a flexible display device according to the related art.
As shown in FIG. 2A, after applying an adhesive to a glass substrate 12, a flexible substrate 16 of a stainless foil or a plastic film is formed on the adhesive 14. Then, thin film arrays 18 for a display device are formed on the flexible substrate 16. As shown in FIG. 2B, the adhesive 14 on a back side of the flexible substrate 16 is then removed to separate the flexible substrate 16 from the glass substrate 12 and the adhesive 14. However, the flexible display device fabricated by a fabrication process shown in FIGS. 2A and 2B has a problem in that the flexible substrate 16 is bent in a separation direction when the adhesive 14 is separated.
To solve the above problem, a flexible display device is formed by a fabrication process shown in FIGS. 3A and 3B. FIGS. 3A and 3B illustrate yet another method for fabricating a substrate of a flexible display device according to the related art.
Referring to FIG. 3A, by coating a plastic thin film on a glass substrate 22 by spin coating, the flexible substrate 26 is formed. Then, thin arrays 28 are formed on the flexible the substrate 26. As shown in FIG. 3B, the glass substrate 22 is then removed from a back side of the flexible substrate 26 by full surface etching. However, since the flexible substrate 26 of the plastic thin film coated by spin coating cannot withstand a pressure applied during a step of attachment to a driving device by itself, a protective film is temporarily attached to the flexible substrate 26. Although a protective film is used, the pad portion cannot be protected since the protective film is attached to a region excluding a pad portion to which the driving device is attached.